One promise—affordability— smashed into millions more pieces this morning. As technical failures bedevil the rollout of President Obama’s health care law, evidence is emerging that one of the program’s loftiest goals — to encourage competition among insurers in an effort to keep costs low — is falling short for many rural Americans.While competition is intense in many populous regions, rural areas and small towns have far fewer carriers offering plans in the law’s online exchanges. Those places, many of them poor, are being asked to choose from some of the highest-priced plans in the 34 states where the federal government...